The Demon's Demon
by Catsoniate
Summary: After Ciel is injured and almost dead, Bill Cipher appears and offers Ciel a deal. A chance to live in return for using Ciel's body as a vessel. Ciel accepts and has to wait for Sebastian to figure out what has happened. And find a way to give him his body back. (Rated T for Bill)
1. Chapter 1

(Just a fanfiction idea that came to my head while watching Gravity Falls and then Kuroshitsuji. Bill possesses Ciel.)

Ciel looked around at the grey surroundings that looked like his home before it burnt down. Then suddenly a glowing triangle appeared in front of him. "Hey there kid, so I see that you're looking for a way out of this tricky situation you're in" He said and Ciel took a step away from him. "What are you?" He asked and the triangle looked at him with his one huge eye. "The names Bill Cipher kid. And I'm a dream demon. I can help you out of this situation all I ask in return is a small… Favour" The demons eye suddenly flashed red then went back to its usual white colour.

Ciel frowned. "What type of favour?" He asked suspicious of him. "Okay kid I'm going to be straight with you. I can't enter the human world without a vessel. And you however would be the perfect vessel. And if you agree to be my vessel then I can help you out. So… Do we have a deal?" He asked and the triangle's hand was enveloped in a bright blue flame. "So if I shake your hand? You'll take over my body. But you'll help me escape?" He asked and Bill nodded. "Yep. A deal's a deal after all" He said and Ciel hesitated before a serious look came across his face. "Deal" And then Ciel shook the demons hand, and cried out in pain as he was suddenly torn from his body.


	2. Chapter 2

Bill opened his eyes and looked around at what appeared to be Ciel's bedroom. It was then that Sebastian opened the door. "Ah young master you're awake. I had thought it would take you a little longer to recover after your fall" Sebastian said and Bill Smirked darkly. "Oh yeah right of course had a little bit of a tumble but I'm a Phantom after all I'm fine." He said and got out of the bed looking around the giant room. "Do you mean a Phantom _hive_ young master?" He asked and Bill looked up at him. "Oh yeah that as well" Bill said then ran to Ciel's closet ignoring the pleasant sensation of pain in his left leg, as he pulled out some of Ciel's clothes. "What? Just blue? Doesn't the kid own anything of another colour?" He asked himself then rolled his eyes and put on some of the clothes messily.

Sebastian walked up to him and helped him neaten them. "Young master you should not be moving around so quickly with your leg still being injured." Sebastian said but Bill quickly just pushed him away laughing. "Don't be ridiculous, Raven I'll be fine" Bill said and turned around leaving the room and a shocked Sebastian behind. "Cipher" Sebastian said and glared his eyes turning bright red as he followed the dream demon. "Took you long enough Raven" Bill said and turned to Sebastian his usually blue eye now bright yellow. "Leave my young master's body at once Cipher." Sebastian ordered making Bill laugh. "Oh that's cute Raven. But compared to be you're barely more then I child in the demon world no matter how old you look. And besides I made a deal with the watchdog. I keep him alive and he gives me his body. And you know what happens if I go back on a deal" He said smirking and Sebastian glared.

They both went downstairs and Bill was immediately hugged by Elizabeth. "Lady Elizabeth. I did not know you were visiting the young master today" Sebastian said as Bill laughed and looked down at Elizabeth. "Hey kid do you want to know the exact date and time of your death? Because if you don't stop hugging me now _it's going to be very soon_ " Bill said and Elizabeth immediately let go of him backing away. "I was just worried about you Ciel. After all you broke your leg yesterday and now you're running around on it" She said. "Well I'm fine kiddo but you need to stop hugging people" Bill said and smirked madly then went to his office and was quickly followed by Sebastian. "Ciph-" Sebastian was cut off by Bill. "You know Raven thanks to this contract mark you still have to call me your master" Bill said and Sebastian growled angrily. " _Young Master_ you have mission for the queen that Ciel was supposed to complete." Sebastian said and Bill frowned. "What but I don't want to. I need to get about creating the end of the world hear!" He said frowning and crossed his arms over his chest. "Well I am sorry _young master_ but it is your duties as the queens guard dog" Sebastian said and smirked at him. "Ugh fine. But we're going hopping first I can't wear just blue it's not a good colour on me" He said and Sebastian frowned. "And how do you intend to pay for your new clothes?" Sebastian asked. "The watchdog is rich remember Raven. It shouldn't be that hard" Bill said and smirked darkly. "So come on let's get going" He added and left the office grabbing Ciel's top hat on his way out the door as Sebastian dejectedly followed, wondering how to give Ciel back his body.


End file.
